Vitamin D: Food, Sun, & Supplements
Vitamin D is an important hormone (yes, it’s a hormone) not only to bone health but also cardiovascular health, reducing hypertension, reducing cholesterol, and helping your body heal from insulin resistance. Some studies also show a correlation between obesity and vitamin D deficiency. But back to bone health…you can take in all the calcium in the world, but you really need vitamin D to assist your bones in absorbing that calcium.
Are you getting the minimum?
The recommended daily allowance (RDA) for vitamin D is 600 international unit (iu) for individuals up to 70 years of age. For those past 70, it goes up to 800 iu per day. Most people that take a multivitamin-mineral supplement (MVM) will get this amount through their MVM. People that don’t take an MVM…well there’s always food and the sun 🙂 We’ll talk about the other ways in a bit.
But is 600-800 iu enough? For many, no it isn’t. For instance, I have a genetic mutation that blunts my vitamin D receptor. This means I have to take triple the amount of vitamin D just to maintain the lower acceptable limits, which is 30 nanograms per milliliter (ng/mL). Even at 30 ng/mL, many people experience fatigue as those amounts aren’t enough for them. In functional nutrition, we really like to see levels around 70 ng/mL.
Vitamin D’s role in health
Aside from potential disease prevention, Vitamin D plays a significant role in the anti-microbial pathway in the body. For instance, research has shown that respiratory tract infections increased, regardless of the season, as vitamin D levels in the body decreased. Additionally, barrier cells, like those lining your lungs, gut, and skin, have an impaired anti-microbial pathway in the presence of low vitamin D. Vitamin D may also promote antiviral activity as well. None of this means you should take vitamin D at the onset of an illness. This just shows that keeping a constant level of vitamin D is important to your system’s overall health.
Ways to Get Vitamin D
Aside from a supplement, there are two other ways you can get vitamin D. The first we’ll hit on is food. Foods like fatty fish, beef liver (yuck!), cheese, egg yolks, and fortified cereals, milks, and juices all contain vitamin D. This becomes a bit trickier for vegans. Foods such as fortified tofu and fortified non-dairy milks contain vitamin D. Mushrooms grown in the sun do as well; they actually absorb UVB rays like our skin. But most vegans will get their vitamin D from non-food places such as a MVM or the sun.
The sun is another. Most people in the south can synthesize about 10,000-20,000 iu with 5-30 minutes of midday sun exposure during the hotter months (ranges vary based on location and amount of pigment in the skin). The definition of sun exposure in this context would be the majority of your skin exposed to the sun with no sunscreen on. Notice I said in the south, midday sun, and hotter months. Morning and afternoon sun produces less UVB rays and the farther north you go, you’ll find fewer UVB rays even in the summer. I also said hotter months versus summer months because it gets warm enough in March in Miami to produce enough vitamin D but it’s technically not summer. Following these guidelines, 2-3 days outside and you’ll have enough vitamin D without supplementing. This is exactly what I do. During the colder months, I supplement and during the hotter months, I go for the outdoors exposure. A bonus is feeling relaxed, getting some fresh air, and taking myself back to some form of nature….even if it is poolside
What plays a role in insufficiency or deficiency?
Various studies have shown individuals with darker skin have reduced absorption of UVB rays into the skin. In turn, this reduces the amount of vitamin D precursor available in the liver to convert to vitamin D. So, individuals that do not have fair skin will have a harder time absorbing enough UVB rays for adequate vitamin D exposure. This doesn’t mean it can’t be done.
Additionally, we spend more hours indoors now that we ever have. We work ridiculously long hours, then come home to do chores, cook dinner, cart the kids around, or just soak up some “me” time in front of the television. These actions coupled with American’s notoriously poor diets, and you’ve got a recipe for limited vitamin D intake/exposure.
On top of that, we have been scared out of our wits about the possibility of developing melanoma. And we should be scared of it. Melanoma is no joke! But because of this, we’ve taken to shellacking ourselves in sunscreen every chance we get. Sunscreen blocks UVB rays thus blocking our skin’s ability to soak up the rays and provide us with the vitamin D we need. Perhaps try adding sunscreen after you’ve been outside for 15-30 minutes?
Conversely, those living above the 37th parallel will have a difficult time making enough vitamin D from sun exposure most of the year. Thus, dietary intake and supplementation are the only routes to maintain vitamin D levels for these folks.
Pay attention to what you’re getting in your diet, expose your skin to the sun, and supplement if needed. Also, ask your physician to test your levels next time you’re in. This will give you a good baseline. It’s a test I request on all my clients!
Remember…health starts from within!
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4. Tangpricha, V. (2007). Vitamin D Deficiency in the Southern United States. Southern Medical Journal, 100(4), 384–385.